The modern automotive engine may lose its coolant by any one of several means. It may have a blown head gasket, a warped head, a cracked block, a leaking freeze plug, a heating core leak, a radiator leak or a lost pet cock.
The engine will overheat rapidly as the coolant disappears. Additionally, coolant within the crankcase leads to rapid corrosion and coolant within a cylinder prevents ignition. For all of these reasons, coolant leaks must be repaired.
Correcting these sources of leaks may be quite expensive, including the removal of the engine. Serious leaks are often so expensive to repair that an entirely new engine or new radiator is required.
For many years cooling system sealants have been marketed with the objective of stopping the leak without incurring the substantial expense of automotive repairs.
At the present time, the following products are on the market: Wynn's "Radiator Stop Leak", K & W "Permanent Metallic Block Seal", "Bar's Leaks" (Extra Strength), Prestone "Heavy Duty Sealer and Stop Leak" and Dupont "#7 Formula Stop Leak" (Bordons).
Many of the prior art products are designed for temporary purposes. They will work for a few hours or days to enable a car to return home from a trip. These products rely upon solid particles to enter small holes or cracks and block the passageway.
In time, the solid particle may break down, thus allowing coolant to pass through the hole. The sealant may also plug up the small tubes in the radiator, thus reducing its effectiveness.